DEVELOPMENT OF FLY ASH USAGE IN THAILAND

DEVELOPMENT OF FLY ASH USAGE IN THAILAND
Somnuk TANGTERMSIRIKUL, Professor
Sirindhorn International Institute of Technology, Thammasat University
ABSTRACT: This paper describes the situation of fly ash usage in Thailand. Firstly, the general
information including typical characteristics of fly ash in Thailand is given. Properties of fly ash in
Thailand were compared with those of the fly ash in Japan in terms of chemical composition and physical
properties. It was found that generally fly ash in Thailand has higher CaO content, higher alkali content
but lower silica content and LOI while fineness of the Thai fly ash was generally lower. It was also found
that water requirement of both countries fly ashes was about the same. Regarding strength, the Thai fly
ash was slightly better. The consumption of fly ash in Thailand increases significantly after the economic
crisis in 1997 and at present almost all fly ash produced in Thailand is used as cement replacing material in
concrete industry. The paper also describes problem at the early stage of introducing fly ash into the
construction industry together with the strategies to promote its use. Finally, examples of application of
fly ash in various types of concrete and cementitious products in Thailand are given.
KEYWORDS: Fly ash, cement replacement, pozzolan, concrete
1. INTRODUCTION
Fly ash is one of the by-products produced from
the process of coal burning. Electricity
generating using coal as the energy source is the
main industry which produces fly ash as its major
solid waste. There are still other types of solid
wastes produced from the coal generating plants
like bottom ash and gypsum but their volumes are
generally far less than that of the fly ash. There are
difficulties around the world to achieve effective
utilization of fly ash or even to get rid of it.
Majority of the fly ash is dumped or used in
low-valued methods such as using as a land-fill
material, soil improvement, road base, land
reclamation, raw material for producing cement.
Some high-valued methods of using are available
such as used as fertilizer, as filler in plastics and
resins, as metal matrix composite (ceramic
additives) [1], etc., but only a little amount of fly
ash can be consumed in such utilization. The
most effective use of fly ash at present, by
considering both volume and value, is still in the
area of concrete. The use of fly ash as a cement
substituting material is believed to be beneficial by
various reasons. In regard of environment, the
cement substitution reduces the depletion of
natural resources used for cement production. It
also reduces the energy used for clinkerization,
then reduces the gases emitted to the environment
especially CO 2 . It is estimated that abut 1 ton of
CO 2 is released per a ton of clinker produced [2].
Although some properties of fly ash concrete, such
as initial strength, carbonation and freezing and
thawing resistance, have been found to be inferior
than the concrete without fly ash, the use of fly ash
to partially replace cement improves many
properties of concrete especially durability
properties such as increasing workability and
pumpability, improving long-term strength,
reducing temperature, reducing shrinkage,
improving resistance against chloride-induced steel
corrosion, increasing sulfate resistance, reducing
risk due to alkali-aggregate reaction, etc
[3,4,5,6,7,8,9]. A proper use of fly ash based on
the type of construction work and the service
environment that the constructed structure is
located is considered to be most rational.
Though there have been worldwide studies,
indicating the benefit of using fly ash in concrete,
fly ash has still not been effectively utilized in
most countries until now due to many reasons. In
Thailand, fly ash has been domestically available
since the end of the 1970’s. However, the use in
concrete was just started in early 1990’s and the
effective use of fly ash was just materialized in
1997. At present (2005), almost all fly ash
produced in Thailand is used as a partial cement
substitution material for both quality improvement
and cost reduction of concrete. The author
believed that Thailand is one of the most
successful countries in regard of the effective use
of fly ash in concrete industry. This paper states
the efforts of the author and his colleagues in
Thailand in paving ways for the construction
societies in Thailand to the effective use of fly ash.
2. GENERAL INFORMATION ON FLY
ASH IN THAILAND
The amount of fly ash produced annually is
approximately 3 million tons during the past 10
years. About 95% of the total production is
produced from the Mae Moh generating plant of
the Electricity Generating Authority of Thailand in
Lampang province, in the north of Thailand. The

est of fly ashes are produced near Bangkok. In
this section, some comparative studies are
conducted to compare the general trend of
characteristics of fly ash produced in Thailand and
Japan.
2.1 Typical characteristics of fly ash in
Thailand
2.1.1 Chemical Composition
Table 1 compares the ranges of chemical
composition of fly ash in Japan and Thailand.
The data of Thai fly ashes are those observed
continuously for more than 10 years. The data of
Japanese fly ashes, though were obtained from a
single study, covered large enough sample types
and sources i.e. 40 types of fly ash from 24
generating plants in Japan [10]. It can be seen
that the chemical composition of fly ash in
Thailand covers a wider range than that of Japan.
This is mainly because, in addition of the
differences of the types of the plants and processes,
Thailand uses many sources of coal both local and
imported ones. The biggest local source is in
Mae Moh, Lampang province, which is located in
the north of Thailand. The coal used in Mae Moh
is lignite while most of the imported coals are
anthracite or bituminous coals. It is noted that for
the Mae Moh fly ash, which comprises of 95% of
the total fly ash produced in Thailand, the
scattering of the chemical composition is not
much.
From Table 1, most of the Thai fly ashes have
lower SiO 2 content, larger CaO and alkali content
than the Japanese fly ash. Though the data on
SO 3 content of the Japaneses fly ash does not
appear in the Table, it is realized that most of the
Thai fly ashes have rather high SO 3 content. It
must be noted here that the high CaO and high SO 3
fly ash mostly belongs to the Mae Moh power
plant where lignite coal is used.
Table 1 Comparison of Chemical Compostion between Fly Ashes in Japan and Thailand
Composition Japan* (%) Thailand** (%)
SiO 2
CaO
Al 2 O 3
Fe 2 O 3
SO 3
MgO
(Na 2 O+0.658K 2 O)
47-70
0.49-7.55
15.64-32.03
2.54-15.68 (majority

2.2 Properties of Paste, Mortars and Concrete
using Fly Ash
2.2.1 Water Requirement
Table 3 shows the comparison of water
requirement between the Thai fly ashes and the
Japanese fly ashes. It should be noted here that
the test methods of both countries are not the same
(JIS A6201-1991 was used to test the Japanese fly
ashes and ASTM C311 was used to test the Thai
fly ash). Mix proportion of the test samples,
apparatus and the test procedure are all different.
Especially for the mix proportion, in JIS
A6201-1991, the water to binder ratio of the
control sample (cement only mortar) is set at 0.65
and the sand to binder ratio is 2.0 while ASTM
C311 specifies water to binder ratio of 0.484 and
sand to binder ratio of 2.75. However, though
both countries’ fly ashes were tested based on
different standards but they have the same concept
to evaluate the test results. If the two set of data
are compared by discarding the difference of the
test methods, then both countries’ fly ashes have
similar water requirement as can be seen from
Table 3. The lower loss on ignition makes the
Thai fly ashes have similar level of water
requirement to the Japanese fly ashes though they
are coarser.
Table 3 Comparison of Water Requirement between Fly Ashes in Japan and Thailand
Properties Japan* (%) Thailand** (%)
Water requirement (%of
the control)
91-105 (majority

2.3 Fly Ash Consumption in Thailand
Fig.1 shows the fly ash consumption in concrete in
Thailand. The consumption shown in the figure
is only for those used as a cement replacing
material in concrete. In Thailand, up to the time
this report is being written, almost 100% of the fly
ash consumption is for this purpose. It is
expected that the consumption of fly ash in cement
and concrete will still increase in the future.
3000000
2500000
2000000
1500000
1000000
1000000
800000
1400000
1800000
2300000
2700000
500000
0
400000
400 1000 2200 15460
'94 '95 '96 '97 '98 '99 '00 '01 '02 '03 '04
Fly ash consumption (tons)
Fig.1 Fly ash consumption in concrete in Thailand
(The value of year 2000 is the forecasted one)
Fig.2 and Fig.3 show the statistics of fly ash used in
various types of concrete. It can be seen from Fig.2
that up to 1997, fly ash was used mostly to produce
special concrete like self- compacting concrete, sulfate
resisting concrete and low heat concrete for mass
concreting. However, the situation changes in 1999
when fly ash was used mostly in normal concrete.
This expressed that fly ash had become more and
more popular and engineers were more and more
confident with the fly ash application in concrete at
that time. At present, fly ash has already become a
conventional cement replacing material in Thailand so
that majority of the ready-mixed concrete plants,
including those in precast concrete and on-site ready
mixed plants, are using it as a major cementitious
material and fly ash concrete has now become a
conventional concrete in Thailand.
LHC
SRC
4%
SCC
5%
NC
8% Others
1%
SRC
SCC
LHC
82%
NC
Others
Fig.2 Distribution of fly ash used in various types of concrete from 1994-1997
LHC:Low heat concrete, SRC:Sulfate resisting concrete,
SCC:Self compacting concrete, NC:Normal concrete

LHC
NC
46%
Others
12%
SRC
SCC
SCC
2%
SRC
5%
LHC
35%
NC
Others
Fig.3 Distribution of fly ash used in various types of concrete in 1999
(forecasted from January to April 1999)
LHC:Low heat concrete, SRC:Sulfate resisting concrete,
SCC:Self-compacting concrete, NC:Normal concrete
3. PROBLEMS AND STRATEGIES TO
PROMOTE THE USE OF FLY ASH
3.1 Problems
During 1980’s, the image of fly ash produced from
Mae Moh was negative due to many researchers’
reports which pointed out the volume instability of
concrete using fly ash due to high SO 3 content in
the fly ash (mostly in the range of higher than 5%
by weight of the fly ash) [12, 13]. Therefore the
uses of fly ash at that time were in the low-value
manners such as used for soil improvement, for
embankment slope stability, for sub-base of
pavement, for concreting of temporally pavement,
etc. It was until the early 1990’s that the SO 3
content of fly ash became lower to conservative
values of below 5%. From that time, various
intensive researches were restarted and many
merits were found from using the fly ash in
concrete as mentioned earlier in the section of
introduction. In spite of the positive study results,
fly ash was very little used in concrete production
until 1997 (see Fig.1) due to many reasons as
follows.
1) Lack of understanding and knowledge on
fly ash among the engineers
2) Doubt on fly ash quality and its
consistency
3) No systematic supplying system to
facilitate the use.
3.2 Strategies
Many efforts were made by the Committee on
Concrete and Materials of the Engineering Institute
of Thailand to promote the use of fly ash in
Thailand.
3.2.1 Research
An original research group consisting of
researchers from 7 universities in Thailand was
formed to study the properties of fly ash and
concrete using fly ash. By this original group,
more than 30 research reports and more than 100
technical papers had been already published until
2000. After that many other universities also
started to conduct research on fly ash and many
more publications have been produced since then.
3.2.2 Education and Training
From 1994 to 2001, eight seminars were arranged,
by the committee, in various places around the
country to give information and educate engineers
on the effective use of fly ash in concrete. A
learn-on-line project was created by the
cooperation between the National Science and
Technology Development Agency, the Electricity
Generating Authority of Thailand and the Joint
Research Group to provide information in a more
effective and broadened way [14]. Many books
and documents were also published for the purpose
of educating engineers in the country [11,15]
3.2.3 Support for Real Practice
Various efforts were made to provide support for
real application as follows
1) Conducting demonstration construction
using fly ash concrete. Many
demonstration construction projects were
conducted during 1992 to 1996 (see Figs.
4, 5 and 6) to provide information.

2) Set up a unit called “By-Product Business
Unit” at the Mae Moh generating plant for
supplying business and quality control of
fly ash. For quality control, the fine coal
used for boiler burning is blended from
various locations and layers of coal mines
in Mae Moh in order to both satisfy the
requirement of energy output and obtain
fly ash with constant properties. At the
moment, the measured properties of fly
ash for quality control at Mae Moh are
CaO, SiO 2 and SO 3 contents. It is
expected that fineness will be another
measured value for quality control at Mae
Moh in the near future. Since fly ash is
not an industrial product but a by-product,
the qualities of fly ash is expected to vary
and be not constant like cement. The
variation in properties is one of the main
hurdles for fly ash using in many parts of
the world, not excepting Thailand. This
system of quality control at the origin
together with the coal blending technique
will help reducing the uncertainty of fly
ash quality and provide confidence to the
users.
3) Provision of standard for fly ash. One of
the problems at the beginning of fly ash
application is the lack of appropriate
standard that suited the local fly ash.
According to many foreign standards, the
properties of Thai fly ash especially the
Mae Moh fly ash did not pass the
requirement on fineness. However,
researches had proved that though the fly
ash had low fineness, it provided very
satisfactory performance when used in
concrete. Many performances are even
better than fly ashes from many other
countries. The committee on concrete
and materials of the Engineering Institute
of Thailand then decided to draft a new
standard specification for fly ash in
Thailand based on properties of Thai fly
ashes and was published in 2003 [16].
Tables 5, 6 and 7 summarize the classes of
fly ash and the corresponding chemical
and physical requirements according to
the latest Thai specification.
4) Produced references for practical
engineers. Two books were published
for being used as references for practical
engineers [11,15].
5) A software “FACOMP T1.0” was
developed as a tool to facilitate the
practical engineers for mix proportioning
of fly ash concrete (see Fig.7).
6) Encouraged ready-mixed concrete
company to launch special fly ash
concrete products such as marine concrete,
sulfate-resisting concrete, sulfate-resisting
concrete, self-compacting concrete,
low-heat concrete, etc.
Item
Properties
Table 5 Chemical properties
First class
Type a
Requirement
Second class
Type b
Third class
1 Silicon dioxide (SiO 2 ), min. % 30.0 30.0 30.0 30.0
2 Calcium oxide (CaO), % - Less than 10.0
Not less than
10.0
-
3 Sulfur trioxide (SO 3 ), max. % 5.0 5.0 5.0 5.0
4 Moisture content, max. % 3.0 3.0 2.0 3.0
5 LOI content, max. % 6.0 1) 6.0 1) 6.0 1) 12.0
Note: 1) The use of fly ash with up to 12% LOI may be approved if either acceptable performance records or
laboratory test results are made available.

Table 6 Chemical properties (optional)
Requirement
Item
Properties
First class
Second class
Type a Type b
Third class
1
Alkali content (Na 2 O + 0.658K 2 O) 1) , max. %
1.1 when SO 3 between 3.0 to 5.0 %
1.2 when SO 3 less than 3.0 %
1.5
4.0
1.5
4.0
1.5
4.0
1.5
4.0
Note: 1) Fly ash with alkali content exceeding this limitation may be approved if the test results on control of
alkali-silica reaction satisfy the requirement.
Table 7 Physical properties
Item Properties First
Requirement
Second class
class Type a Type b
Third class
1
Fineness (select a method)
Amount retained on 45-μm-mesh sieve, max. %
Or Blaine fineness, min. cm 2 /g
10
6000
50
2300
55
2000
65
1600
2
Strength activity index 1) with OPC type 1
7-day, min. % of the control
85
28-day, min. % of the control
95
91-day, min. % of the control 2) 100
70
75
85
70
75
85
60
70
75
3 Water requirement, max. % of the control 102 105 105 108
4 Autoclave expansion 3) , max. % 0.8 0.8 0.8 0.8
Fig.4 Demonstration of mass concreting using fly ash concrete at Mae Moh power generating plant

Fig.5a Concrete wall
Fig.5b Concrete box culvert
Fig.5 Demonstration of Self-Compacting Concrete using fly ash at Mae Moh power generating plant
Fig.6 Demonstration construction of Roller-Compacted Concrete Pavement using fly ash at Mae Moh
power generating plant

Fig.7 A computer software for mix proportioning of fly ash concrete
4. APPLICATION OF FLY ASH IN
CONCRETE
Fly ash has become a popular cement replacing
materials for concrete application since 1997 (see
Fig.1) after the country faced economic crisis.
One of the main reasons is that the cost of fly ash
is much lower than that of the cement. The
immediate gain from the low cost of fly ash could
overcome the more
4.1 Ready-Mixed Concrete
For ready-mixed concrete, fly ash is normally used
to replace cement in the ranges of 20 to 30% by
weight of the total cementitious materials. Fly
ash concrete has become conventional concrete for
ready-mixed concrete industry. As mentioned
above, many ready-mixed concrete companies
started to launch special concrete products with fly
ash such as marine concrete, sulfate-resisting
concrete, sulfate-resisting concrete,
self-compacting concrete, low-heat concrete, since
late 1990’s. Some high volume fly ash concrete
were also practiced in Thailand with the maximum
fly ash content up to 55% of the total binders for
self-compacting concrete, 47.5% for low-heat
concrete and 68% for roller-compacted concrete
(see Fig.8 for Pak Mool dam constructed using
roller-compacted concrete). The ready-mixed
concrete industry is currently the major consumer
of fly ash in Thailand.
Fig.8 Pak Mool dam in Ubol Rachathani constructed using roller-compacted concrete with fly ash content
of 68% of the total cementitious materials.

4.2 Precast Concrete, Concrete Products
For precast concrete and concrete product
industries, fly ash is normally used in the works
that does not require early strength such as
non-prestressed concrete works. For prestressed
concrete industries, fly ash is also used but with a
maximum cement replacement of only up to 10%.
The exception may be in the case of
self-compacting concrete application in which fly
ash may be used up to a range of 30% to 50% even
in prestressed concrete work..
4.3 Other Cementitious Products
Some cementitious material products which use fly
ash to replace cement in the production are such as
cementitious fibered roof tile, cementitious fibered
panel, etc. In this category, fly ash is normally
used up to a maximum of 30% of the total
cementitious materials.
4.4 Blended Cement
Some cement companies have made efforts to
introduce ready-blended fly ash cement into the
concrete market in Thailand. Most of them are
introduced in the form of cement for durability
purposes such as cement for marine environment
having high resistance against sulfate attack and
chloride-induced steel corrosion, sulfate-resisting
cement or low-heat cement, etc. However, these
cements are still not popular especially for project
constructions using ready-mixed concrete. For
projects, where ready-mixed concrete is usually
applied, it is more popular to mix fly ash at the
ready-mixed concrete plants. This is because 1)
ready-blended fly ash cement is more expensive
than cement with fly ash as a separate binder, 2)
the ratio of fly ash is usually adjusted according to
the required performances of concrete when it is
used as a separate binder.
4.5 Repair Materials
Fly ash is also used in enhancing performances and
reducing cost of some repair materials especially
for grouting materials. Fly ash has also been
studied as a stabilizer and to control expansion of
expansive cement [17].
5. CONCLUDING REMARKS
Based on what mentioned in this paper, it can be
said that Thailand has become a very successful
country in regard of fly ash usage in concrete
industry. The success was obtained on great
efforts and good strategic planning and patience of
a number of academicians and professional
engineers. The use of fly ash has also become
one of the significant factors to change the concept
of concrete practice in Thailand from that
considering strength only to considering both
strength and durability.
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